영어 모의고사 (자동 편성)

Every cell in the human body follows an internal timer known as the circadian rhythm, a roughly twenty-four-hour cycle ①that governs when we feel alert and when we feel drowsy. This clock is regulated primarily by a tiny cluster of neurons in the brain ②that responds to light entering through the eyes. When morning sunlight strikes the retina, the cluster signals the body ③to suppress sleep hormones and raise body temperature, preparing us for activity. As evening approaches and light fades, the same mechanism triggers the release of melatonin, a hormone ④promotes drowsiness. Because this rhythm evolved around the natural cycle of day and night, modern habits such as staying indoors under artificial light or working night shifts can push the internal clock out of sync with the external environment. Such misalignment does not simply cause tiredness; it has also ⑤been associated with digestive problems and reduced concentration, suggesting that timing matters as much as total sleep hours.

Sleep hygiene refers to a set of simple daily habits that ①helps the body prepare for consistent, restorative rest. Experts commonly recommend going to bed and waking up at the same time every day, even on weekends, because an irregular schedule confuses the body's internal clock and makes it ②harder to fall asleep on demand. They also advise reserving the bedroom for sleep alone, since using the bed to study, scroll through a phone, or watch videos teaches the brain ③to associate that space with wakeful activity rather than rest. Physical environment matters as well: a cool, dark, and quiet room tends ④to produce deeper sleep than one that is warm, bright, or noisy. None of these individual habits guarantees a good night's sleep on its own, but together they form a routine that gradually trains the body to expect and enter sleep more easily, much the way a consistent set of cues trains an athlete's body ⑤to perform at a certain time each day.

Social psychologists describe a phenomenon called the bystander effect, in which individuals become less likely to help a victim as the number of witnesses ①increases. Each observer assumes someone else will step in, and this diffusion of responsibility leaves no one willing to act. Cyberbullying ②minimizes this problem, since a single humiliating post can be witnessed by thousands of people scattered across the internet rather than a few standing nearby. Anonymity ③intensifies the effect further, allowing silent observers to scroll past cruel comments without feeling accountable for their inaction. Some bystanders even worry that intervening publicly might make them the bully's next target, so they choose to remain ④silent instead. However, silence signals approval to both the bully and the audience watching the exchange unfold. Experts insist that even a single supportive comment can ⑤disrupt this harmful pattern.

As millions of people now earn income through delivery apps and ride-hailing platforms, questions about their legal status have become increasingly ①urgent. Most platform workers are classified as independent contractors rather than employees, which means they lack access to minimum wage guarantees, paid sick leave, and unemployment insurance. Companies ②oppose this arrangement because it allows them to avoid the costs associated with hiring full employees. Worker advocates argue that many platform workers ③depend on these jobs as their primary source of income, much like traditional employees do. Several countries have recently begun ④reconsidering their labor laws, proposing new categories that would grant platform workers some employee-like protections. Supporters of these reforms believe fair treatment and flexibility can ⑤coexist within the same system.

A short nap taken in the early afternoon, often called a power nap, can noticeably sharpen attention and mood without leaving a person ①refreshed afterward. The key lies in timing: naps limited to roughly twenty minutes allow the brain to pass through the ②lightest stages of sleep while avoiding the deeper stages associated with slow-wave activity. If a nap extends much beyond that window, the sleeper risks waking during deep sleep, which produces a ③foggy, disoriented feeling known as sleep inertia that can persist for thirty minutes or more. Laboratory studies comparing napping and non-napping groups have ④repeatedly shown that a brief nap improves reaction time and short-term memory almost as effectively as a full night of extra rest. Interestingly, the benefit appears ⑤strongest when the nap occurs several hours after waking, since this is when the body's natural dip in alertness makes rest most effective.

Across the world, teenagers are chronically short on sleep, often getting two or three hours less than the eight to ten hours experts recommend for their age. (A) In response, some school districts have experimented with delaying start times, and early results suggest that students who gain extra rest show improved grades and better mood. (B) As a result, chronic sleep loss during adolescence has been linked to impaired concentration, weakened memory, and a higher risk of anxiety and depression. (C) Part of the problem lies in biology, since the body's internal clock naturally shifts later during puberty, while school start times rarely adjust to match.

Wearable devices that track sleep have become enormously popular, promising a detailed breakdown of light, deep, and REM sleep each night. (A) Despite these limitations, many users have come to treat the nightly score generated by their device as an objective medical verdict, sometimes experiencing anxiety when the number falls below what they expect, a phenomenon researchers have begun calling orthosomnia. (B) Independent studies comparing wearable data with polysomnography, the gold-standard method used in clinical sleep labs, have found that consumer devices are reasonably accurate at distinguishing sleep from wakefulness but considerably less reliable at identifying specific sleep stages. Some trackers overestimate deep sleep, while others underestimate the amount of time spent in REM sleep, and the margin of error can vary widely between brands. (C) These gadgets typically rely on movement sensors and heart rate monitors to estimate sleep stages, since directly measuring brain activity would require equipment found only in a sleep laboratory. This indirect approach, however, introduces significant uncertainty.

The rapid rise of the gig economy has led researchers to examine both its opportunities and its risks. (A) In addition, because their income depends heavily on the number of tasks completed, many gig workers find it difficult to save money consistently. (B) On the positive side, gig platforms allow workers to set their own schedules and take on projects that match their skills. (C) Yet this freedom comes at a price, since most gig workers are not entitled to employer-provided benefits like health insurance.

These physiological adjustments, though subtle, translate into a noticeable difference once competition actually begins. Skipping a proper warm-up before intense exercise might seem like a harmless way to save a few minutes, but the practice carries real physiological costs. ( ① ) A cold muscle is stiffer and less elastic than a warm one, making it considerably more prone to strains and tears when suddenly asked to contract forcefully. ( ② ) Gradually raising body temperature through light activity increases blood flow to the muscles, allowing oxygen to reach tissue more efficiently and enabling nerve signals to travel faster between the brain and the muscle fibers. A proper warm-up also raises heart rate gradually, easing the cardiovascular system into strenuous work rather than shocking it with a sudden demand. ( ③ ) Athletes who warm up thoroughly tend to report better performance in the early minutes of competition, since their bodies are already primed rather than adjusting on the fly. ( ④ ) For this reason, coaches treat warm-up routines not as optional preparation but as an essential part of training itself. ( ⑤ )

This connection is not merely correlational; sleep appears to directly supply the raw materials the immune system needs. When the body fights off an infection, the immune system relies heavily on adequate sleep to function effectively. ( ① ) During deep sleep, the body produces and releases cytokines, proteins that help regulate immune responses and coordinate the fight against harmful invaders such as viruses and bacteria. ( ② ) People who consistently sleep fewer than six hours a night show measurably weaker antibody responses after vaccination compared with those who sleep seven or eight hours, suggesting that sleep loss can blunt the immune system's ability to build lasting protection. ( ③ ) Chronic sleep deprivation also appears to promote low-grade inflammation throughout the body, a state that, over time, has been linked to a higher risk of heart disease and other chronic conditions. ( ④ ) Rather than being a passive state in which the body simply rests, sleep functions as an active period during which the immune system repairs itself and prepares for future threats. ( ⑤ ) This is why doctors often recommend extra sleep, not just medication, when someone is fighting an illness.